The present invention relates to a nut for a fastening arrangement for fixing an item to a structural component, the nut having an axially aligned socket for a bolt, which can be joined to the structural component, and the socket having an opening, via which the bolt can be introduced into the socket.
The present invention further relates to a fastening arrangement for fixing an item to a structural component, comprising a bolt which is joined to the structural component in a longitudinal (axial) direction, and a nut which is fixed to the bolt, the nut having a flange section, and the item being fixed between the flange section and the structural component and/or between the flange section and a flange of the bolt.
Finally the present invention relates to a method of fastening an item to a structural component, particularly for producing a fastening arrangement, comprising steps in which a nut is slipped on to an upper side of a bolt joined to a structural component and the nut is then driven on to the bolt by means of a blow in a longitudinal direction, the item being fixed between a flange section of the nut and the structural component and/or a flange of the bolt.
Fastening arrangements of the aforementioned type are used in motor vehicle construction, for example. By means of such a fastening arrangement or a plurality of such fastening arrangements it is possible, for example, to attach flat panelling elements to the underbody of a vehicle.
In doing this a first step is to join a bolt perpendicularly to a surface of the structural component (such as an underbody sheet metal panel) in order to produce a fastening arrangement. This can be done, for example, by means of so-called stud welding, but it can also be accomplished by adhesive bonding methods or thermoplastic welding methods. In the case of stud welding the bolt and the structural component are generally made of a metal material. In the case of adhesive bonding the bolt and the structural component may also be of any other materials. In the case of thermoplastic welding the bolt and the structural component are generally made of plastic.
In a known method of producing a fastening arrangement of the aforementioned type the bolt joined to the structural component is a threaded bolt having a metric thread. The nut is correspondingly a threaded nut having a corresponding metric internal thread. In order to fasten the item it is placed on the structural component, the bolt protruding through a recess in the item. The nut is then screwed on to the threaded bolt.
Alternatively, another known method is to drive bolt nuts on to such bolts. If the bolt is made of a metal material, the nut in this case may be made of a plastic material, for example. In this case the nut is first slipped onto the upper side of the bolt and is then pressed by means of a blow (with a hammer, for example) axially on to the bolt. Here the nut is formed with a coarse screw thread on its inner circumference, for example.
Although driven assembly makes the actual assembly operation easier, since it obviates the need for a rotating movement of the nut, the quality of the fastening arrangement produced in this way largely depends on whether the nut has previously been correctly slipped on to the upper side of the bolt.
If the driven nut has a coarse screw thread on its inner circumference, fluctuations can furthermore occur in the holding forces attainable.
In this context, an object of the invention is to specify an improved nut, an improved fastening arrangement and an improved method of fastening.
In the case of the nut specified in the introductory part, this object is achieved in that in the area around the opening the nut has at least one depression, which is designed so that a radially elastic holding section is formed between the opening and the depression.
In the case of the fastening arrangement specified in the introductory part the object is achieved in that the nut is a nut according to the invention.
In the case of the method specified in the introductory part this object is achieved in that, in the area of the opening through which the bolt enters the nut, the nut has an elastic holding section, which serves to hold the nut in the time between slipping the nut on to the bolt and driving the nut on to the bolt.
Designing such a nut with an elastic holding section in the edge area of the opening means that prior to final assembly the nut can be securely pre-assembled with relatively high pre-assembly holding forces. Such a nut is generally advantageous if it has a metric internal thread and is screwed on to a threaded bolt in a final assembly step.
This type of pre-assembly is particularly advantageous, however, if the nut is then finally assembled by means of an axial blow. The elastic holding device in this case ensures a precise positioning of the nut in relation to the bolt. Furthermore, the nut cannot accidentally fall off between pre-assembly and final assembly.
The elastic holding device is furthermore also capable of yielding elastically as the nut is driven home, so that the holding device can also help to increase the holding forces after performing the final assembly step. This applies in particular if the bolt is embodied as a threaded bolt (with metric thread or coarse screw thread).
The object is therefore achieved in full.
According to a preferred embodiment the depression is embodied as an annular depression around the opening.
Here the radially elastic holding section is embodied as a thin shank stub, which can yield elastically, radially outwards into the depression and after slipping the nut on can exert radial holding forces acting inwards on the bolt.
However, the depression can also be designed so that the radially elastic holding section has one or more radially elastic retaining tongues distributed in a circumferential direction. In this case the depression is preferably connected on specific sections of the circumference to the opening or a section of the socket.
It is furthermore advantageous overall if the holding section comprises a projection (or lug) projecting radially inwards.
This reduces the inside diameter of the holding section in relation to the inside diameter of the socket. In other words the holding section is radially expanded by the projection bearing against the bolt. The projection here preferably makes the inside diameter of the holding section smaller than the outside diameter of the bolt, particularly a section of the bolt on which the nut is pre-assembled.
The projection on the inner circumference of the holding section may be a single annular ridge. However, a plurality of individual projections distributed over the circumference may also be provided on the inner circumference of the holding section.
It is particularly preferred if the projection is a continuous annular ridge running over the circumference of the holding section.
According to a further embodiment the nut has an introduction taper, which leads into the opening.
This measure makes it easier to slip the nut on to the bolt for the purpose of pre-assembly. The introduction taper here has a large diameter in the area of the underside of the nut, which tapers down to the diameter of the opening of the socket. In this case the larger diameter may be at least twice the diameter of the opening.
It is especially preferred here if the depression is located in the area of the introduction taper.
The holding section here preferably also has a conically tapering shape at its end pointing away from the socket.
This makes it even easier to introduce the bolt into the nut for the purpose of pre-assembly.
It is furthermore advantageous overall if the socket is of circular cross section.
This allows the holding force achieved by the final assembly to be set to a predetermined value with no fluctuations. It is especially preferred here if the socket on its circumference (and/or the nut on its inner circumference) is of substantially smooth design, that is to say without internal thread.
It is furthermore advantageous overall if the socket extends axially right through the nut and if an inspection section extending in a transverse direction thereto, which is destroyed when the bolt is introduced, is formed in the socket.
It can happen, particularly in the so-called driven assembly, that the nut is not driven far enough onto the bolt in an axial direction. In this case the inspection section would not be destroyed. Since the socket passes right though in an axial direction, the inspection section can be inspected after performing the final assembly step, in order to establish whether the nut has been driven far enough on to the bolt.
The inspection section may take the form of a continuous film over the cross-sectional area of the socket, for example, but it may also be formed by a narrow cross web or the like.
It is especially preferred here if the diameter of the socket, in a section on the side of the inspection section remote from the opening, is larger than the diameter of the socket in a section on the side of the inspection section facing the opening.
This serves to improve the fracturing properties of the inspection section.
In the case of the fastening arrangement according to the invention it is particularly advantageous if the bolt is a threaded bolt having a longitudinal groove formed in the threaded area.
Such a threaded bolt may be embodied as a metric bolt having a so-called paint groove, for example.
For the purpose of anticorrosion protection the bolts, especially in motor vehicle engineering, are joined to the vehicle body in the untreated state (particularly in stud welding). The bolt is then painted together with the structural component to which it is fastened.
When screwing a nut on to such a threaded bolt, such a paint groove can ensure that the paint applied does not interfere with the thread engagement.
When driving a nut on to such a bolt it is particularly advantageous if the socket for the bolt is of circular cross section. In this case uniformly high holding forces result irrespective of the relative rotational position between the bolt and the nut.
It goes without saying that the aforementioned features and those yet to be explained below can be used not only in the particular combination specified but also in other combinations or individually without departing from the scope of the present invention.